Manufacture of aromatic nitrogen compounds



Patented Au 32, 1941 MANUFACTURE OF AROMATIC NITRGGEN COMPOUNDS RaphaelRosen, Elizabeth, N. J., assignor to Standard @il Development Company, acorporation of Delaware No Drawing. Application September 20, 1938,Serial No. 230,781

8 Claims.

This invention relates to novel products rich in aromatic nitrogencompounds and methods of preparing and using the same. Moreparticularly, it relates to the nitration of certain petroleumhydrocarbon liquids rich in aromatic hydrocarbons to form a mixture ofaromatic nitro compounds, as Well as the subsequent reduction the nitrocompounds to the corresponding a1 matic amines, which have been foundtohave exceptionally high anti-knock properties for use.

in motor fuels.

By the method of the present invention, pe troleum hydrocarbon fractionsand products derived therefrom by simple physical treatment,

- such as solvent extraction, may be used as the raw materials for theformation of aromatic nitro compounds or aromatic. amines of highquality and in good yields. The mixture of nitro compounds, formed inthe early stages of the process, may be separated from non-aromaticmaterial and further treated for the separation of the individual nitrocompounds, or the mixture may be reduced as such, either in the presenceor absence of parafiinic material, to form a mixture of amines, whichmay in turn be treated for the separation of the individual aromaticamines, or the mixture of amines may be used as such as a valuableanti-knock agent in motor fuels.

It has now been found that a high yield and a high quality product maybe obtained if one selects as the material to be nitrated a petroleumhydrocarbonliquid substantially free from oleflns, because it has beenfound that due to their olefinic structure these compounds interferewith the desired nitration of aromatic compounds, by

, reason of the fact that the olefins undergo oxidation and otherside'reactions much more easily than the aromatic hydrocarbons and hencerequire the consumption of an excessively large amount of nitratingagent in order to accomplish the desired result. Furthermore, whenoxidation products thus formed are present during the second orhydrogenation step, an excessive amount of hydrogenating material isnecessary;

and finally when olefins are present in the starting material, thefinished product (after hydrogenation) has lower anti-knock propertiesthan the product resulting from the treatment of an original rawmaterial rich in aromatics, but substantially free from olefins.

It has been proposed in the Ihrig U. S. Patent 1,844,362 to producearomatic amines by first extracting a petroleum fraction containingaromatic and hydroaromatic hydrocarbons as well as olefins with a polarsolvent to concentrate the aromatic, hydroaromatic and unsaturatedcompounds, then separating from the extract the unsaturated compounds bytreatment with sulfuric acid, and finally nitrating and reducing toproduce a mixture of amines. This method has the disadvantage that thesulfuric acid treatment removes not only the olefins but also aconsiderable proportion of the valuable aromatic hydrocarbons as well.It is well known that benzene, toluene, and the xylenes dissolve readilyin strong sulfuric acid. It has, in fact, been found that benzene,toluene, and mixed xylenes are, respectively, 27%, and 98% soluble in93% sulfuric acid in 10 minutes of contact. (J. Inst. Petr. TechnoL,vol. 17 (1931), page 140.) Furthermore, aromatic hydrocarbons, such astoluene, have been found to be very readily attacked by sulfuric acid inthe presence of olefins. (Gurwitsch and Moore, The Scientific Principlesof Petroleum Technology (1932), page 393.) It is evident, therefore,that the 93% sulfuric acid employed in the process of the Ihrig patentwould dissolve considerable quantities of the aromatic hydrocarbons fromthe sulfur dioxide extracts containing high concentrations of thearomatics and olefins.

The sulfuric acid treatment, moreover, is not efllcient in removing allof the olefinic material from the oil. It has been found that sulfuricacid causes considerable polymerization of olefins and that thepolymerization products are unsaturated and dissolve in the oil layer,rather than the acid layer. (Gurwitsch and Moore, ibid., page 395.)within the oil considerable quantities of unsaturated olefinic materialwhich would absorb a part of the nitrating acid and occasion otherdisadvantageous results hereinbefore discussed.

The presentinvention avoids these disadvantages by selecting as theinitial raw material for the preparation of nitro compounds and amines apetroleum hydrocarbon liquid, which is rich in aromatics butsubstantially free from olefinic hydrocarbons and therefore requires notreatment with sulfuric acid. As suitable materials one may usestraight-run aromatic rich petroleum distillates derived from crudepetroleum containing relatively large amounts of aromatic hydrocarbonsbut substantially no olefins, such as the crudes obtained from theConroe, Deep Sand Raccoon Bend, Shallow Sand Raccoon Bend, or Tomballfields; or one may use liquids resulting from a hydrogenation treatmentof a highly aromatic cracked petroleum fraction containing ole- Thus theacid treatment would still leave I conditions tending to produceprimarily mono- A nitrated derivatives as the nitration is completed, inorder that the amines resulting from the reduction of the nitrocompounds will have boiling points within the gasoline boiling range,also to avoid the formation of explosive poly-nitrated derivatives. Forthis purpose, temperatures not substantially above room temperatures andproportions of nitric acid not greatly in excess of that required forproducing the mono-nitrated derivatives are used.

The resulting nitro derivatives may, if desired, be segregated from anynon-aromatic constituents present, such as paraffinic hydrocarbons(which do not react with the nitrating agent), by any suitable means,for example, by washing or extraction with a suitable selective solventtherefor, such as ether, or any other suitable treatment which willcause the separation of the mixed liquid into two distinct layers ofdifierent gravity. Poly-nitrates, if present, may be removed from thenitrate layer by washing and steam distilling the latter. The individualnitro compounds composing the mixture may be separated, if desired, byany convenient process, e. g., distillation under reduced pressure.

The aromatic nitro compounds thus obtained, either free from or still inadmixture with paraffinic compounds, may, if desired, be reduced orhydrogenated by any suitable means, such as by the use of finely dividediron in the presence of a small amount of acid, or by treatment with agas rich in hydrogen in the presence of a hydrogenation catalyst, suchas a finely divided active nickel catalyst, formed, for example, by thereduction of nickel oxide or by dissolving out aluminum or silicon froman alloy of nickel with aluminum or silicon by means of sodiumhydroxide. The resulting aromatic amines may either be used while stillin admixture with unreacted nonaromatic compounds or may be separatedtherefrom by steam distillation or by the formation of their salts andsubsequent liberation of the amines by distillation or by suitableextraction methods, and may finally be distilled to a desired boilingrange, for instance, 40-225 C., if the product is to be used as ananti-knock agent in.

motor fuels, or, if the individual amines are desired as end products,these may be separated from the mixture by any suitable means.

As illustrations of suitable methods of carrying out the invention, thefollowing examples are given:

Example I A. naphtha cut, having a boiling range of 99-193 0., obtainedfrom a mixture of aromatic South Texas crude petroleum oils containingsubstantially no oleflns, was extracted with liquid sulfur dioxide. Theresulting extract exhibited a boiling range of 93-146 C. and an A. P. I.gravity of 36.4, and contained approximately 85% aromatic hydrocarbons.To 10 parts by volume of this extract was added 16 parts by volume of amixture of equal parts of concentrated nitric and concentrated sulfuricacid at a temperature of -10 to 0 C., with agitation of the mixture.After a continued agitation at this temperature for 1 /2 hours, themixture was poured into 200 parts by volume of ice water, wherebyseparation of the acid was eifected.

The mixture of nitrated compounds and unreacted hydrocarbons was reducedby treatment with iron filings and hydrochloric acid at -90" (2., withrapid stirring, for about 1 hour. The resulting amines were separated bydistillation with steam and redistilled at 202218 C. A yield ofapproximately 73%, based on the amount of aromatic hydrocarbons presentin the nitrating mixture, was obtained.

Example II One part by volume of a nitrated sulfur dioxide extract of anaromatic type petroleum hydrocarbon liquid, obtained as in Example I,was dissolved in two partsby volume of ethyl alcohol. About 10 grams ofa finely divided active nickel catalyst was added for each cubiccentimeters of solution, and hydrogen was passed in under four poundspressure, with agitation. The temperature rose to about 50 C., andreduction was complete at the end of two hours. A similar test showedthat the hydrogenation could be conducted equally well withoutdissolving the nitrated product in alcohol.

The amines present in the product of the hydrogenation step may beseparated and purified by the methods described in Example I.

A mixture of aromatic amines produced by the method of Example I wastested to determine its anti-knock characteristics when blended withgasoline motor fuels. The tests were conducted both by the method of theAmerican Society for Testing Materials (C. F. R. engine), test designation D435'7-3'7T (A. S. T. M. Standards on Petroleum Products andLubricants), and by the method of the U. S. Army Air Corps (U. S. ArmySpecification 2-94). The results of these tests are set forth in TableI.

Table I U. 8. Army T t A. S. T. M. method method g Blend No. 1 cc.Blend. No. Blend. lead lead value lead value 1 Gasoline .v 15 32.5 2Ditto plus 4% 73 o amines 82. 1 87. 3 252 3 Dittoin plus 7.5% 84- a as 5202 4 Ditto plus 15% 86 0 240 a as 88.0 16 5 Gasoline 13"--. 085.6 2(129.2 188 6 Ditto plus 5% amines 89 153 o Inter-pointed value. H hgrade gasoline motor fuel.

"B end of gasoline containing about 42% isopropyl ether.

lead tetraethyl per U. S.

lhe blending value of the amines is calculated by the following formula:

Ograx 12) Blending va1ue= FA where 'creases the octane number ofnon-leaded as well as leaded gasolines, and that these amines also haveunusually high blending values.

It is not intended that the invention be limited to the particularexamples, modifications, and embodiments of the invention, which havebeen given merely for the sake of illustration, but only by the appendedclaims, in which it is intended to claim all novelty inherent in theinvention as broadly as the prior art permits.

I claim:

1. The process for preparing a composition containing a large proportionof nitro derivatives of aromatic hydrocarbons which comprises extractingwith sulfur dioxide a naphtha fraction of petroleum rich in aromatichydrocarbons, but substantially free from olefins, treating theresulting extract with a mixture of nitric and sulfuric acids, andseparating the nitro compounds formed from the non-aromatic materialpresent.

' 2. The process for preparing a composition containing a largeproportion of mono-nitrated derivatives of aromatic hydrocarbons whichcomprises treating a petroleum hydrocarbon liquid rich in aromatichydrocarbons, but substantially free from olefins, with a suflicientquantity of a mixture of nitric and sulfuric acids to react with all ofthe aromatic hydrocarbons present, but to form substantially onlymono-nitrated derivatives therewith, at a temperature not sub--stantially above room temperature, and separating the nitro compoundsformed from the nonaromatic material present.

3. The process for preparing a composition containing a largeproportionof nitro derivatives of aromatic hydrocarbons which comprisesex tracting with sulfur dioxide a naphthafraction of a petroleum rich inaromatic hydrocarbons, but substantially free from olefins, and having aboiling range of approximately 99-193 0., treating the resulting extractwith a mixture of approximately equal parts of nitric and sulfuric acidsat approximately to 0' C., and separating the nitro compounds formedfrom the non-aromatic material present.

-4. In the process of preparing a composition containing a largeproportion of aromatic amines and adapted to be used as an anti-knockblending agent for motor fuels, by nitrating a hydrocarbon mixturecontaining a substantial pro portion of aromatic hydrocarbons andreducing the aromatic nitro compounds thus formed to aromatic amines,the steps which comprise extracting a naphtha fraction of petroleum richin aromatic hydrocarbons, but substantially free from olefins, with asolvent having a substantially greater solvent power for aromatichydrocarbons than for paraffinic hydrocarbons, and removing said solventfrom the extracted material prior to the nitration step.

5. In the process of preparing ,a composition containing a largeproportion of aromatic amines and adapted to be used as an anti-knockblending agent for motor fuels, by nitrating a hydrocarbon mixturecontaining a substantial proportion of aromatic hydrocarbons andreducing the aromatic nitro compounds thus formed to aromatic amines,the steps which comprise extracting a naphtha fraction of a virginpetroleum hydrocarbon liquid rich in aromatic hydrocarbons, butsubstantially free from olefins, with sulfur dioxide, and removing saidsulfur dioxide from the extracted material prior to the nitration step.i

6. In the process of preparing a composition containing a largeproportion of aromatic amines and adapted to be used as an anti-knockblending agent for motor fuels, by nitrating a hydrocarbon mixturecontaining a substantial proportion of aromatic hydrocarbons andreducing the aromatic nitro compound thus formed to aromatic amines, thesteps which comprise extracting a naphtha fraction of a petroleum richin aromatic hydrocarbons, but substantially free from olefins, andhaving a boiling range of approximately 99-193 0., with sulfur dioxide,and removing said sulfur dioxide from the extracted material prior tothe nitration step.

7. In the process of preparing a composition containing a largeproportion of nitro derivatives of aromatic hydrocarbons by nitrating ahydrocarbon mixture, the steps which comprise extracting a naphthafraction of petroleum rich in aromatic hydrocarbons, but substantiallyfree from olefins, with a solvent having a substantially greater solventpower for aromatic hydrocarbons than for parafiinic hydrocarbons, andremoving said solvent from the extracted material prior to' thenitration step.

8. In the process for preparing a composition containing a largeproportion of nitro derivatives of aromatic hydrocarbons by nitrating ahydrocarbon mixture, the steps which comprise extracting a virginpetroleum hydrocarbon liquid rich in aromatic hydrocarbons, but

substantially free from olefins, with a solvent having a substantiallygreater solvent power for aromatic hydrocarbons than forparafiinichydrocarbons, and removing said solvent from the extracted materialprior to the nitration step.

RAPHAEL ROSEN'.

